System for improving LED illumination reliability in projection display systems

• US 20080007885A1
• Filed: 07/05/2006
• Published: 01/10/2008
• Est. Priority Date: 07/05/2006
• Status: Abandoned Application

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Mehrl, David Joseph, Douglass, Michael Richard
• Application Number:
  US11/481,373
• Publication Number:
  US 20080007885A1
• Time in Patent Office: Days
• US Class Current: 361/104
• CPC Class Codes: H05B 45/40 Details of LED load circuits

Abstract

System and method for increasing the reliability of LED illumination systems used in projection display systems. A preferred embodiment comprises a light source with one or more serially connected sequences of two or more light elements coupled to a power source. Each light element includes a light emitting diode and an antifuse coupled in parallel to the light emitting diode, wherein the antifuse short circuits if a current flowing through the antifuse exceeds a specified magnitude. The current exceeds the specified magnitude only if an open circuit type failure occurs in the light emitting diode and the short circuit of the antifuse creates a low-resistance current path, thereby preserving current flow through the serially connected sequence and keeping the remaining light elements illuminated.

Claims

1. A light source comprising:

a serially connected sequence of two or more light elements coupled to a power source, wherein each light element comprises

a light emitting diode, and

an antifuse coupled in parallel to the light emitting diode, the antifuse configured to short circuit if a current flowing through the antifuse exceeds a specified magnitude.

2. The light source of claim 1, wherein the light source comprises two or more serially connected sequences of light elements, and wherein the sequences of light elements are coupled in parallel.

3. The light source of claim 1, wherein the antifuse has a high resistance when the current flowing through the antifuse is less than the specified magnitude.

4. The light source of claim 1, wherein the antifuse comprises a mixture containing a conductive powder that will melt into a conductor when the current flowing through the antifuse exceeds the specified magnitude.

5. The light source of claim 1, wherein the antifuse comprises an electromechanically active material that deforms when an electric field of a specified magnitude is applied, and wherein the deformation of the antifuse results in the creation of a low-resistance current path through the antifuse.

6. The light source of claim 1, wherein the antifuse comprises:

a thin film resistor, the thin film resistor configured to produce heat proportional to current flowing through a heat sensitive material; and

a heat sensitive material coupled to the thin film resistor, the heat sensitive material configured to deform under the presence of heat and create a low-resistance current path when sufficient heat is produced by the thin film resistor.

7. The light source of claim 1, wherein the antifuse comprises a silicon controlled rectifier, the silicon controlled rectifier configured to begin conducting when a voltage drop across the silicon controlled rectifier exceeds a second specified magnitude.

8. The light source of claim 1 further comprising a fuse coupled in series with the light emitting diode and in parallel with the antifuse, the fuse configured to open circuit if a second current flowing through the fuse exceeds a second specified magnitude.

9. The light source of claim 1, wherein each light emitting diode comprises a sequence of two or more serially coupled light emitting diodes, and wherein the respective antifuse is coupled in parallel to each sequence of serially coupled light emitting diodes.

10. The light source of claim 1, wherein the power source provides power to illuminate the light emitting diodes in the light elements, and wherein the power source adjusts to maintain a substantially consistent current through the remaining light emitting diodes when an antifuse short circuits.

11. A display system comprising:

a light source comprising a serially connected sequence of two or more light elements coupled to a power source, wherein each light element comprises

a light emitting diode, and

an antifuse coupled in parallel to the light emitting diode;

an array of light modulators optically coupled to the light source, wherein the array of light modulators creates images by setting each light modulator in the array to a state for displaying an image on a display plane by modulating light from the light source; and

a controller coupled to the array of light modulators, the controller configured to issue commands to control the operation of the array of light modulators.

12. The display system of claim 11, wherein when the first current is less than the specified magnitude, the antifuse has a high resistance.

13. The display system of claim 12, wherein when the first current exceeds the specified magnitude, the antifuse short circuits.

14. The display system of claim 11, wherein the array of light modulators is a digital micromirror device.

15. The display system of claim 11, wherein the array of light modulators is a liquid crystal display array.

16. The display system of claim 11, wherein the array of light modulators is a liquid crystal on silicon array.

17. A method for bypassing a light emitting diode (LED), the method comprising:

providing a first current through the LED in a first current path;

generating a light with the LED in response to the first current;

when the LED or its connections fail with an open circuit, creating with an antifuse a second current path in parallel with the first current path to bypass the open circuit; and

providing a second current through the second current path.

18. The method of claim 17 further comprising after the generating, when the LED fails with a closed circuit, creating with a fuse in series with the LED a second open circuit.

19. The method of claim 18 further comprising after the creating of the open circuit with the fuse, creating with the antifuse the second current path in parallel with the first current path to bypass the second open circuit and the failed LED.

20. The method of claim 17, wherein the antifuse changes from a high-resistance current path to a low-resistance current path when a current flowing through the antifuse exceeds a specified magnitude.